Conventionally, an electricity storage system to which a plurality of storage batteries are connected is used to obtain a prescribed capacity that cannot be obtained by one storage battery. Performance of the electricity storage system depends on a method for controlling a charge or a discharge of each storage battery.
For example, Patent Document 1 discloses a technology in which, in a power supply system including a solar cell and a plurality of inverters, an inverter acting as a master unit controls operation and stopping of the remaining inverters based on a change in a power generation amount of the solar cell or a change in an AC output amount from the inverters.
However, although the power supply system disclosed in Patent Document 1 can perform the operation without depending on a specific inverter, there is a risk that power cannot efficiently be output because conversion efficiency of the inverter is not considered.